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MPEG-1 Audio Layer II

January 06, 2023

MPEG-1 Audio Layer II or MPEG-2 Audio Layer II (MP2, sometimes incorrectly called Musicam or MUSICAM)[7] is a lossy audio compression format defined by ISO/IEC 11172-3 alongside MPEG-1 Audio Layer I and MPEG-1 Audio Layer III (MP3). While MP3 is much more popular for PC and Internet applications, MP2 remains a dominant standard for audio broadcasting.[8]

MPEG-1 or MPEG-2 Audio Layer II
Filename extension
.mp2
Internet media type
audio/mpeg,[1] audio/MPA[2]
Initial release6 December 1991; 31 years ago (1991-12-06)[3]
Latest release
ISO/IEC 13818-3:1998
April 1998; 24 years ago (1998-04)
Type of formatLossy audio
Contained byMPEG-ES
StandardISO/IEC 11172-3,[4] ISO/IEC 13818-3[5]
Open format?Yes
Free format?Yes[6]
Websitehttp://mpeg.chiariglione.org/standards/mpeg-1/audio

History of development from MP2 to MP3

See also: MP3 § History, and MPEG-1 § Layer II

MUSICAM

MPEG-1 Audio Layer 2 encoding was derived from the MUSICAM (Masking pattern adapted Universal Subband Integrated Coding And Multiplexing) audio codec, developed by Centre commun d'études de télévision et télécommunications (CCETT), Philips, and the Institut für Rundfunktechnik (IRT) in 1989 as part of the EUREKA 147 pan-European inter-governmental research and development initiative for the development of a system for the broadcasting of audio and data to fixed, portable or mobile receivers (established in 1987).

It began as the Digital Audio Broadcast (DAB) project managed by Egon Meier-Engelen of the Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt (later on called Deutsches Zentrum für Luft- und Raumfahrt, German Aerospace Center) in Germany. The European Community financed this project, commonly known as EU-147, from 1987 to 1994 as a part of the EUREKA research program.

The Eureka 147 System comprised three main elements: MUSICAM Audio Coding (Masking pattern Universal Sub-band Integrated Coding And Multiplexing), Transmission Coding & Multiplexing and COFDM Modulation.[9]

MUSICAM was one of the few codecs able to achieve high audio quality at bit rates in the range of 64 to 192 kbit/s per monophonic channel. It has been designed to meet the technical requirements of most applications (in the field of broadcasting, telecommunication and recording on digital storage media) — low delay, low complexity, error robustness, short access units, etc.[10][11]

As a predecessor of the MP3 format and technology, the perceptual codec MUSICAM is based on integer arithmetics 32 subbands transform, driven by a psychoacoustic model. It was primarily designed for Digital Audio Broadcasting and digital TV, and disclosed by CCETT(France) and IRT (Germany) in Atlanta during an IEEE-ICASSP conference.[12] This codec incorporated into a broadcasting system using COFDM modulation was demonstrated on air and on the field [13] together with Radio Canada and CRC Canada during the NAB show (Las Vegas) in 1991. The implementation of the audio part of this broadcasting system was based on a two chips encoder (one for the subband transform, one for the psychoacoustic model designed by the team of G. Stoll (IRT Germany), later known as Psychoacoustic model I in the ISO MPEG audio standard) and a real time decoder using one Motorola 56001 DSP chip running an integer arithmetics software designed by Y.F. Dehery's team (CCETT, France). The simplicity of the corresponding decoder together with the high audio quality of this codec using for the first time a 48 kHz sampling frequency, a 20 bits/sample input format (the highest available sampling standard in 1991, compatible with the AES/EBU professional digital input studio standard) were the main reasons to later adopt the characteristics of MUSICAM as the basic features for an advanced digital music compression codec such as MP3.

The audio coding algorithm used by the Eureka 147 Digital Audio Broadcasting (DAB) system has been subject to the standardization process within the ISO/Moving Pictures Expert Group (MPEG) in 1989–94.[14][15] MUSICAM audio coding was used as a basis for some coding schemes of MPEG-1 and MPEG-2 Audio.[16] Most key features of MPEG-1 Audio were directly inherited from MUSICAM, including the filter bank, time-domain processing, audio frame sizes, etc. However, improvements were made, and the actual MUSICAM algorithm was not used in the final MPEG-1 Audio Layer II standard.

Since the finalisation of MPEG-1 Audio and MPEG-2 Audio (in 1992 and 1994), the original MUSICAM algorithm is not used anymore.[7][17] The name MUSICAM is often mistakenly used when MPEG-1 Audio Layer II is meant. This can lead to some confusion, because the name MUSICAM is trademarked by different companies in different regions of the world.[7][17][18] (Musicam is the name used for MP2 in some specifications for Astra Digital Radio as well as in the BBC's DAB documents.)

The Eureka Project 147 resulted in the publication of European Standard, ETS 300 401 in 1995, for DAB which now has worldwide acceptance. The DAB standard uses the MPEG-1 Audio Layer II (ISO/IEC 11172-3) for 48 kHz sampling frequency and the MPEG-2 Audio Layer II (ISO/IEC 13818-3) for 24 kHz sampling frequency.[19]

MPEG Audio

In the late 1980s, ISO's Moving Picture Experts Group (MPEG) started an effort to standardize digital audio and video encoding, expected to have a wide range of applications in digital radio and TV broadcasting (later DAB, DMB, DVB), and use on CD-ROM (later Video CD).[20] The MUSICAM audio coding was one of 14 proposals for MPEG-1 Audio standard that were submitted to ISO in 1989.[11][16]

The MPEG-1 Audio standard was based on the existing MUSICAM and ASPEC audio formats.[21] The MPEG-1 Audio standard included the three audio "layers" (encoding techniques) now known as Layer I (MP1), Layer II (MP2) and Layer III (MP3). All algorithms for MPEG-1 Audio Layer I, II and III were approved in 1991 as the committee draft of ISO-11172[22][23][24] and finalized in 1992[25] as part of MPEG-1, the first standard suite by MPEG, which resulted in the international standard ISO/IEC 11172-3 (a.k.a. MPEG-1 Audio or MPEG-1 Part 3), published in 1993.[4] Further work on MPEG audio[26] was finalized in 1994 as part of the second suite of MPEG standards, MPEG-2, more formally known as international standard ISO/IEC 13818-3 (a.k.a. MPEG-2 Part 3 or backward compatible MPEG-2 Audio or MPEG-2 Audio BC[27]), originally published in 1995.[5][28] MPEG-2 Part 3 (ISO/IEC 13818-3) defined additional bit rates and sample rates for MPEG-1 Audio Layer I, II and III. The new sampling rates are exactly half that of those originally defined for MPEG-1 Audio. MPEG-2 Part 3 also enhanced MPEG-1's audio by allowing the coding of audio programs with more than two channels, up to 5.1 multichannel.[26]

The Layer III (MP3) component uses a lossy compression algorithm that was designed to greatly reduce the amount of data required to represent an audio recording and sound like a decent reproduction of the original uncompressed audio for most listeners.

Emmy Award in Engineering

CCETT (France), IRT (Germany) and Philips (The Netherlands) won an Emmy Award in Engineering 2000 for development of a digital audio two-channel compression system known as Musicam or MPEG Audio Layer II.[29][30]

Technical specifications

MPEG-1 Audio Layer II is defined in ISO/IEC 11172-3 (MPEG-1 Part 3)

  • Sampling rates: 32, 44.1 and 48 kHz
  • Bit rates: 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320 and 384 kbit/s

An extension has been provided in MPEG-2 Audio Layer II and is defined in ISO/IEC 13818-3 (MPEG-2 Part 3)[31][32]

  • Additional sampling rates: 16, 22.05 and 24 kHz
  • Additional bit rates: 8, 16, 24, 40 and 144 kbit/s
  • Multichannel support - up to 5 full range audio channels and an LFE-channel (Low Frequency Enhancement channel)

The format is based on successive digital frames of 1152 sampling intervals with four possible formats:

  • mono format
  • stereo format
  • intensity encoded joint stereo format (stereo irrelevance)
  • dual channel (uncorrelated) format

Variable bit rate

MPEG audio may have variable bit rate (VBR), but it is not widely supported. Layer II can use a method called bit rate switching. Each frame may be created with a different bit rate.[32][33] According to ISO/IEC 11172-3:1993, Section 2.4.2.3: To provide the smallest possible delay and complexity, the (MPEG audio) decoder is not required to support a continuously variable bit rate when in layer I or II.[34]

How the MP2 format works

See also: MPEG-1 § Layer II
  • MP2 is a sub-band audio encoder, which means that compression takes place in the time domain with a low-delay filter bank producing 32 frequency domain components. By comparison, MP3 is a transform audio encoder with hybrid filter bank, which means that compression takes place in the frequency domain after a hybrid (double) transformation from the time domain.
  • MPEG Audio Layer II is the core algorithm of the MP3 standards. All psychoacoustical characteristics and frame format structures of the MP3 format are derived from the basic MP2 algorithm and format.
  • The MP2 encoder may exploit inter channel redundancies using optional "joint stereo" intensity encoding.
  • Like MP3, MP2 is a perceptual coding format, which means that it removes information that the human auditory system will not be able to easily perceive. To choose which information to remove, the audio signal is analyzed according to a psychoacoustic model, which takes into account the parameters of the human auditory system. Research into psychoacoustics has shown that if there is a strong signal on a certain frequency, then weaker signals at frequencies close to the strong signal's frequency cannot be perceived by the human auditory system. This is called frequency masking. Perceptual audio codecs take advantage of this frequency masking by ignoring information at frequencies that are deemed to be imperceptible, thus allowing more data to be allocated to the reproduction of perceptible frequencies.
  • MP2 splits the input audio signal into 32 sub-bands, and if the audio in a sub-band is deemed to be imperceptible then that sub-band is not transmitted. MP3, on the other hand, transforms the input audio signal to the frequency domain in 576 frequency components. Therefore, MP3 has a higher frequency resolution than MP2, which allows the psychoacoustic model to be applied more selectively than for MP2. So MP3 has greater scope to reduce the bit rate.
  • The use of an additional entropy coding tool, and higher frequency accuracy (due to the larger number of frequency sub-bands used by MP3) explains why MP3 does not need as high a bit rate as MP2 to get an acceptable audio quality. Conversely, MP2 shows a better behavior than MP3 in the time domain, due to its lower frequency resolution. This implies less codec time delay — which can make editing audio simpler — as well as "ruggedness" and resistance to errors which may occur during the digital recording process, or during transmission errors.
  • The MP2 sub-band filter bank also provides an inherent "transient concealment" feature, due to the specific temporal masking effect of its mother filter. This unique characteristic of the MPEG-1 Audio family implies a very good sound quality on audio signals with rapid energy changes, such as percussive sounds. Because both the MP2 and MP3 formats use the same basic sub-band filter bank, both benefit from this characteristic.

Applications of MP2

Part of the DAB digital radio and DVB digital television standards.

Layer II is commonly used within the broadcast industry for distributing live audio over satellite, ISDN and IP Network connections as well as for storage of audio in digital playout systems. An example is NPR's PRSS Content Depot programming distribution system. The Content Depot distributes MPEG-1 L2 audio in a Broadcast Wave File wrapper. MPEG2 with RIFF headers (used in .wav) is specified in the RIFF/WAV standards. As a result, Windows Media Player will directly play Content Depot files, however, less intelligent .wav players often do not. As the encoding and decoding process would have been a significant drain on CPU resources in the first generations of broadcast playout systems, professional broadcast playout systems typically implement the codec in hardware, such as by delegating the task of encoding and decoding to a compatible soundcard rather than the system CPU.

All DVD-Video players in PAL countries contain stereo MP2 decoders, making MP2 a possible competitor to Dolby Digital in these markets. DVD-Video players in NTSC countries are not required to decode MP2 audio, although most do. While some DVD recorders store audio in MP2 and many consumer-authored DVDs use the format, commercial DVDs with MP2 soundtracks are rare.

MPEG-1 Audio Layer II is the standard audio format used in the Video CD and Super Video CD formats (VCD and SVCD also support variable bit rate and MPEG Multichannel as added by MPEG-2).

MPEG-1 Audio Layer II is the standard audio format used in the MHP standard for set-top boxes.

MPEG-1 Audio Layer II is the audio format used in HDV camcorders.

MP2 files are compatible with some Portable audio players.

Naming and extensions

The term MP2 and filename extension .mp2 usually refer MPEG-1 Audio Layer II data, but can also refer to MPEG-2 Audio Layer II, a mostly backward compatible extension which adds support for multichannel audio, variable bit rate encoding, and additional sampling rates, defined in ISO/IEC 13818-3. The abbreviation MP2 is also sometimes erroneously applied to MPEG-2 video or MPEG-2 AAC audio.

Licensing

Sisvel S.p.A., a Luxembourg-based company, administers licenses for patents applying to MPEG Audio.[35]

See also

Notes

  1. ^ "The audio/mpeg Media Type - RFC 3003". IETF. November 2000. Retrieved 2009-12-07.
  2. ^ "MIME Type Registration of RTP Payload Formats – RFC 3555". IETF. July 2003. Retrieved 2009-12-07.
  3. ^ Patel K, Smith BC, Rowe LA (1993-09-01). "Performance of a software MPEG video decoder". Proceedings of the First ACM International Conference on Multimedia. ACM Multimedia. New York City: Association for Computing Machinery: 75–82. doi:10.1145/166266.166274. ISBN 978-0-89791-596-0. Reference 3 in the paper is to Committee Draft of Standard ISO/IEC 11172, December 6, 1991.
  4. ^ a b "ISO/IEC 11172-3:1993 – Information technology — Coding of moving pictures and associated audio for digital storage media at up to about 1,5 Mbit/s — Part 3: Audio". ISO. 1993. Retrieved 2010-07-14.
  5. ^ a b "ISO/IEC 13818-3:1995 – Information technology — Generic coding of moving pictures and associated audio information — Part 3: Audio". ISO. 1995. Retrieved 2010-07-14.
  6. ^ MPEG-1 and MPEG-2 Layer II Audio Encoding (Partial draft). Sustainability of Digital Formats. Washington, D.C.: Library of Congress. 17 May 2012. Retrieved 1 December 2021.
  7. ^ a b c "MPEG Audio FAQ Version 9". 1998. Retrieved 2010-08-22.
  8. ^ Techopedia. "MPEG-1 Audio Layer II (MP2)". techopedia.com. Retrieved 2022-03-17.
  9. ^ A J Bower (1998). "Digital Radio — The Eureka 147 DAB System". UK: BBC. Retrieved 2010-08-22.
  10. ^ Dehery, Y.F.; Lever, M.; Urcun, P. (1991). "A MUSICAM source codec for digital audio broadcasting and storage". [Proceedings] ICASSP 91: 1991 International Conference on Acoustics, Speech, and Signal Processing. pp. 3605–3608 vol.5. doi:10.1109/ICASSP.1991.151054. ISBN 0-7803-0003-3.
  11. ^ a b "AES E-Library – Musicam Source Coding". 1991. Retrieved 2010-08-22.
  12. ^ Dehery, Y.F.; Lever, M.; Urcun, P. (May 1991). A MUSICAM source codec for Digital Audio Broadcasting and storage. [Proceedings] ICASSP 91: 1991 International Conference on Acoustics, Speech, and Signal Processing. pp. 3605–3608. doi:10.1109/ICASSP.1991.151054.
  13. ^ Box, Alan (1991-04-15). "A DAB commentary from Alan Box, EZ communication and chairman NAB DAB task force" (PDF). Broadcasting. Vol. 150, no. 15. p. 26.
  14. ^ Digital Audio Broadcasting (DAB); DAB to mobile, portable and fixed receivers – Details of 'DE/JTC-DAB' Work Item – ETS 300 401, 1995-02-15, retrieved 2010-08-23
  15. ^ (PDF), 1992, archived from the original (PDF) on 2005-05-04, retrieved 2010-08-22
  16. ^ a b . 1990. Archived from the original on 2010-02-14. Retrieved 2010-08-22.
  17. ^ a b Telos Systems. . Archived from the original on 2001-05-08. Retrieved 2010-08-22.
  18. ^ MUSICAM USA. "MUSICAM USA Frequently Asked Questions – Isn't MUSICAM simply your implementation of ISO/MPEG Layer 2?". Retrieved 2010-08-23.
  19. ^ Radio Broadcasting Systems; Digital Audio Broadcasting (DAB) to mobile, portable and fixed receivers – Details of 'REN/JTC-DAB-36' Work Item – EN 300 401, 2006-06-15, retrieved 2010-08-23
  20. ^ Chiariglione, Leonardo (October 1989). . Kurihama: Moving Picture Experts Group. Archived from the original on 2010-08-05..
  21. ^ Digital Video and Audio Broadcasting Technology: A Practical Engineering Guide (Signals and Communication Technology) ISBN 3-540-76357-0 p. 144: "In the year 1988, the MASCAM method was developed at the Institut für Rundfunktechnik (IRT) in Munich in preparation for the digital audio broadcasting (DAB) system. From MASCAM, the MUSICAM (masking pattern universal subband integrated coding and multiplexing) method was developed in 1989 in cooperation with CCETT, Philips and Matsushita."
  22. ^ Chiariglione, Leonardo (November 1991). . Kurihama: Moving Picture Experts Group. Archived from the original on 2011-05-03. Retrieved 2010-07-17.
  23. ^ ISO (November 1991). . neuron2.net. Archived from the original (DOC) on June 11, 2010. Retrieved 2010-07-17.
  24. ^ Patel, Ketan; Smith, Brian C.; Rowe, Lawrence A. Performance of a Software MPEG Video Decoder (PDF). ACM Multimedia 1993 Conference. Article's reference 3 is: 'ISO/IEC JTC/SC29, "Coded Representation of Picture, Audio and Multimedia/Hypermedia Information", Committee Draft of Standard ISO/IEC 11172, December 6, 1991'.
  25. ^ ISO (1992-11-06). . Chiariglione.org. Archived from the original on 12 August 2010. Retrieved 2010-07-17.
  26. ^ a b (Press release). International Organization for Standardization. 1993-04-02. Archived from the original on 2010-08-06. Retrieved 2010-07-18.
  27. ^ ISO (October 1998). "MPEG Audio FAQ Version 9 - MPEG-1 and MPEG-2 BC". ISO. Retrieved 2009-10-28.
  28. ^ Brandenburg, Karlheinz; Bosi, Marina (February 1997). "Overview of MPEG Audio: Current and Future Standards for Low-Bit-Rate Audio Coding". Journal of the Audio Engineering Society. 45 (1/2): 4–21. Retrieved 30 June 2008.
  29. ^ (PDF), archived from the original (PDF) on 2010-04-14, retrieved 2010-08-01
  30. ^ . 2001-02-11. Archived from the original on 2001-02-11. Retrieved 2010-08-01.
  31. ^ Werner Oomen, Leon van de Kerkhof. "MPEG-2 Audio Layer I/II". chiariglione.org. Retrieved 2009-12-29.
  32. ^ a b Predrag Supurovic (September 1998). "MPEG Audio Frame Header". Retrieved 2009-07-11.
  33. ^ ISO MPEG Audio Subgroup, MPEG Audio FAQ Version 9, MPEG-1 and MPEG-2 BC, retrieved on 2009-07-11.
  34. ^ TwoLAME: MPEG Audio Layer II VBR, retrieved on 2009-07-11.
  35. ^ "Sisvel | We protect ideas - MPEG Audio - Introduction". sisvel.com. Retrieved 2021-07-04.

References

  • Genesis of the MP3 Audio Coding Standard by Hans Georg Musmann in IEEE Transactions on Consumer Electronics, Vol. 52, Nr. 3, pp. 1043–1049, August 2006
  • MUSICAM Source Coding by Yves-François Dehery, AES 10th International Conference: Kensington, London, England, (7-9 Sept 1991), pp 71–79.

External links

  • The history of MP3 from Fraunhofer IIS
  • TooLAME – An MP2 encoder
  • TwoLAME – A fork of the tooLAME code
  • RFC 3003 – The document defining MIME type for MPEG-1 Audio Layer II
  • – Source code for small open source decoder.
  • Official MPEG web site
  • – Some information about patents

January 06, 2023
mpeg, audio, layer, this, article, includes, list, general, references, lacks, sufficient, corresponding, inline, citations, please, help, improve, this, article, introducing, more, precise, citations, december, 2016, learn, when, remove, this, template, messa. This article includes a list of general references but it lacks sufficient corresponding inline citations Please help to improve this article by introducing more precise citations December 2016 Learn how and when to remove this template message MPEG 1 Audio Layer II or MPEG 2 Audio Layer II MP2 sometimes incorrectly called Musicam or MUSICAM 7 is a lossy audio compression format defined by ISO IEC 11172 3 alongside MPEG 1 Audio Layer I and MPEG 1 Audio Layer III MP3 While MP3 is much more popular for PC and Internet applications MP2 remains a dominant standard for audio broadcasting 8 MPEG 1 or MPEG 2 Audio Layer IIFilename extension mp2Internet media typeaudio mpeg 1 audio MPA 2 Initial release6 December 1991 31 years ago 1991 12 06 3 Latest releaseISO IEC 13818 3 1998April 1998 24 years ago 1998 04 Type of formatLossy audioContained byMPEG ESStandardISO IEC 11172 3 4 ISO IEC 13818 3 5 Open format YesFree format Yes 6 Websitehttp mpeg chiariglione org standards mpeg 1 audio Contents 1 History of development from MP2 to MP3 1 1 MUSICAM 1 2 MPEG Audio 1 3 Emmy Award in Engineering 2 Technical specifications 2 1 Variable bit rate 3 How the MP2 format works 4 Applications of MP2 5 Naming and extensions 6 Licensing 7 See also 8 Notes 9 References 10 External linksHistory of development from MP2 to MP3 EditSee also MP3 History and MPEG 1 Layer II MUSICAM Edit MPEG 1 Audio Layer 2 encoding was derived from the MUSICAM Masking pattern adapted Universal Subband Integrated Coding And Multiplexing audio codec developed by Centre commun d etudes de television et telecommunications CCETT Philips and the Institut fur Rundfunktechnik IRT in 1989 as part of the EUREKA 147 pan European inter governmental research and development initiative for the development of a system for the broadcasting of audio and data to fixed portable or mobile receivers established in 1987 It began as the Digital Audio Broadcast DAB project managed by Egon Meier Engelen of the Deutsche Forschungs und Versuchsanstalt fur Luft und Raumfahrt later on called Deutsches Zentrum fur Luft und Raumfahrt German Aerospace Center in Germany The European Community financed this project commonly known as EU 147 from 1987 to 1994 as a part of the EUREKA research program The Eureka 147 System comprised three main elements MUSICAM Audio Coding Masking pattern Universal Sub band Integrated Coding And Multiplexing Transmission Coding amp Multiplexing and COFDM Modulation 9 MUSICAM was one of the few codecs able to achieve high audio quality at bit rates in the range of 64 to 192 kbit s per monophonic channel It has been designed to meet the technical requirements of most applications in the field of broadcasting telecommunication and recording on digital storage media low delay low complexity error robustness short access units etc 10 11 As a predecessor of the MP3 format and technology the perceptual codec MUSICAM is based on integer arithmetics 32 subbands transform driven by a psychoacoustic model It was primarily designed for Digital Audio Broadcasting and digital TV and disclosed by CCETT France and IRT Germany in Atlanta during an IEEE ICASSP conference 12 This codec incorporated into a broadcasting system using COFDM modulation was demonstrated on air and on the field 13 together with Radio Canada and CRC Canada during the NAB show Las Vegas in 1991 The implementation of the audio part of this broadcasting system was based on a two chips encoder one for the subband transform one for the psychoacoustic model designed by the team of G Stoll IRT Germany later known as Psychoacoustic model I in the ISO MPEG audio standard and a real time decoder using one Motorola 56001 DSP chip running an integer arithmetics software designed by Y F Dehery s team CCETT France The simplicity of the corresponding decoder together with the high audio quality of this codec using for the first time a 48 kHz sampling frequency a 20 bits sample input format the highest available sampling standard in 1991 compatible with the AES EBU professional digital input studio standard were the main reasons to later adopt the characteristics of MUSICAM as the basic features for an advanced digital music compression codec such as MP3 The audio coding algorithm used by the Eureka 147 Digital Audio Broadcasting DAB system has been subject to the standardization process within the ISO Moving Pictures Expert Group MPEG in 1989 94 14 15 MUSICAM audio coding was used as a basis for some coding schemes of MPEG 1 and MPEG 2 Audio 16 Most key features of MPEG 1 Audio were directly inherited from MUSICAM including the filter bank time domain processing audio frame sizes etc However improvements were made and the actual MUSICAM algorithm was not used in the final MPEG 1 Audio Layer II standard Since the finalisation of MPEG 1 Audio and MPEG 2 Audio in 1992 and 1994 the original MUSICAM algorithm is not used anymore 7 17 The name MUSICAM is often mistakenly used when MPEG 1 Audio Layer II is meant This can lead to some confusion because the name MUSICAM is trademarked by different companies in different regions of the world 7 17 18 Musicam is the name used for MP2 in some specifications for Astra Digital Radio as well as in the BBC s DAB documents The Eureka Project 147 resulted in the publication of European Standard ETS 300 401 in 1995 for DAB which now has worldwide acceptance The DAB standard uses the MPEG 1 Audio Layer II ISO IEC 11172 3 for 48 kHz sampling frequency and the MPEG 2 Audio Layer II ISO IEC 13818 3 for 24 kHz sampling frequency 19 MPEG Audio Edit In the late 1980s ISO s Moving Picture Experts Group MPEG started an effort to standardize digital audio and video encoding expected to have a wide range of applications in digital radio and TV broadcasting later DAB DMB DVB and use on CD ROM later Video CD 20 The MUSICAM audio coding was one of 14 proposals for MPEG 1 Audio standard that were submitted to ISO in 1989 11 16 The MPEG 1 Audio standard was based on the existing MUSICAM and ASPEC audio formats 21 The MPEG 1 Audio standard included the three audio layers encoding techniques now known as Layer I MP1 Layer II MP2 and Layer III MP3 All algorithms for MPEG 1 Audio Layer I II and III were approved in 1991 as the committee draft of ISO 11172 22 23 24 and finalized in 1992 25 as part of MPEG 1 the first standard suite by MPEG which resulted in the international standard ISO IEC 11172 3 a k a MPEG 1 Audio or MPEG 1 Part 3 published in 1993 4 Further work on MPEG audio 26 was finalized in 1994 as part of the second suite of MPEG standards MPEG 2 more formally known as international standard ISO IEC 13818 3 a k a MPEG 2 Part 3 or backward compatible MPEG 2 Audio or MPEG 2 Audio BC 27 originally published in 1995 5 28 MPEG 2 Part 3 ISO IEC 13818 3 defined additional bit rates and sample rates for MPEG 1 Audio Layer I II and III The new sampling rates are exactly half that of those originally defined for MPEG 1 Audio MPEG 2 Part 3 also enhanced MPEG 1 s audio by allowing the coding of audio programs with more than two channels up to 5 1 multichannel 26 The Layer III MP3 component uses a lossy compression algorithm that was designed to greatly reduce the amount of data required to represent an audio recording and sound like a decent reproduction of the original uncompressed audio for most listeners Emmy Award in Engineering Edit CCETT France IRT Germany and Philips The Netherlands won an Emmy Award in Engineering 2000 for development of a digital audio two channel compression system known as Musicam or MPEG Audio Layer II 29 30 Technical specifications EditMPEG 1 Audio Layer II is defined in ISO IEC 11172 3 MPEG 1 Part 3 Sampling rates 32 44 1 and 48 kHz Bit rates 32 48 56 64 80 96 112 128 160 192 224 256 320 and 384 kbit sAn extension has been provided in MPEG 2 Audio Layer II and is defined in ISO IEC 13818 3 MPEG 2 Part 3 31 32 Additional sampling rates 16 22 05 and 24 kHz Additional bit rates 8 16 24 40 and 144 kbit s Multichannel support up to 5 full range audio channels and an LFE channel Low Frequency Enhancement channel The format is based on successive digital frames of 1152 sampling intervals with four possible formats mono format stereo format intensity encoded joint stereo format stereo irrelevance dual channel uncorrelated formatVariable bit rate Edit MPEG audio may have variable bit rate VBR but it is not widely supported Layer II can use a method called bit rate switching Each frame may be created with a different bit rate 32 33 According to ISO IEC 11172 3 1993 Section 2 4 2 3 To provide the smallest possible delay and complexity the MPEG audio decoder is not required to support a continuously variable bit rate when in layer I or II 34 How the MP2 format works EditSee also MPEG 1 Layer II MP2 is a sub band audio encoder which means that compression takes place in the time domain with a low delay filter bank producing 32 frequency domain components By comparison MP3 is a transform audio encoder with hybrid filter bank which means that compression takes place in the frequency domain after a hybrid double transformation from the time domain MPEG Audio Layer II is the core algorithm of the MP3 standards All psychoacoustical characteristics and frame format structures of the MP3 format are derived from the basic MP2 algorithm and format The MP2 encoder may exploit inter channel redundancies using optional joint stereo intensity encoding Like MP3 MP2 is a perceptual coding format which means that it removes information that the human auditory system will not be able to easily perceive To choose which information to remove the audio signal is analyzed according to a psychoacoustic model which takes into account the parameters of the human auditory system Research into psychoacoustics has shown that if there is a strong signal on a certain frequency then weaker signals at frequencies close to the strong signal s frequency cannot be perceived by the human auditory system This is called frequency masking Perceptual audio codecs take advantage of this frequency masking by ignoring information at frequencies that are deemed to be imperceptible thus allowing more data to be allocated to the reproduction of perceptible frequencies MP2 splits the input audio signal into 32 sub bands and if the audio in a sub band is deemed to be imperceptible then that sub band is not transmitted MP3 on the other hand transforms the input audio signal to the frequency domain in 576 frequency components Therefore MP3 has a higher frequency resolution than MP2 which allows the psychoacoustic model to be applied more selectively than for MP2 So MP3 has greater scope to reduce the bit rate The use of an additional entropy coding tool and higher frequency accuracy due to the larger number of frequency sub bands used by MP3 explains why MP3 does not need as high a bit rate as MP2 to get an acceptable audio quality Conversely MP2 shows a better behavior than MP3 in the time domain due to its lower frequency resolution This implies less codec time delay which can make editing audio simpler as well as ruggedness and resistance to errors which may occur during the digital recording process or during transmission errors The MP2 sub band filter bank also provides an inherent transient concealment feature due to the specific temporal masking effect of its mother filter This unique characteristic of the MPEG 1 Audio family implies a very good sound quality on audio signals with rapid energy changes such as percussive sounds Because both the MP2 and MP3 formats use the same basic sub band filter bank both benefit from this characteristic Applications of MP2 EditPart of the DAB digital radio and DVB digital television standards Layer II is commonly used within the broadcast industry for distributing live audio over satellite ISDN and IP Network connections as well as for storage of audio in digital playout systems An example is NPR s PRSS Content Depot programming distribution system The Content Depot distributes MPEG 1 L2 audio in a Broadcast Wave File wrapper MPEG2 with RIFF headers used in wav is specified in the RIFF WAV standards As a result Windows Media Player will directly play Content Depot files however less intelligent wav players often do not As the encoding and decoding process would have been a significant drain on CPU resources in the first generations of broadcast playout systems professional broadcast playout systems typically implement the codec in hardware such as by delegating the task of encoding and decoding to a compatible soundcard rather than the system CPU All DVD Video players in PAL countries contain stereo MP2 decoders making MP2 a possible competitor to Dolby Digital in these markets DVD Video players in NTSC countries are not required to decode MP2 audio although most do While some DVD recorders store audio in MP2 and many consumer authored DVDs use the format commercial DVDs with MP2 soundtracks are rare MPEG 1 Audio Layer II is the standard audio format used in the Video CD and Super Video CD formats VCD and SVCD also support variable bit rate and MPEG Multichannel as added by MPEG 2 MPEG 1 Audio Layer II is the standard audio format used in the MHP standard for set top boxes MPEG 1 Audio Layer II is the audio format used in HDV camcorders MP2 files are compatible with some Portable audio players Naming and extensions EditThe term MP2 and filename extension mp2 usually refer MPEG 1 Audio Layer II data but can also refer to MPEG 2 Audio Layer II a mostly backward compatible extension which adds support for multichannel audio variable bit rate encoding and additional sampling rates defined in ISO IEC 13818 3 The abbreviation MP2 is also sometimes erroneously applied to MPEG 2 video or MPEG 2 AAC audio Licensing EditSisvel S p A a Luxembourg based company administers licenses for patents applying to MPEG Audio 35 See also EditMPEG 1 MPEG 1 Audio Layer I MPEG 1 Audio Layer III MPEG 2 MP4 container format Elementary stream Musepack originally MP2 based with numerous improvementsNotes Edit The audio mpeg Media Type RFC 3003 IETF November 2000 Retrieved 2009 12 07 MIME Type Registration of RTP Payload Formats RFC 3555 IETF July 2003 Retrieved 2009 12 07 Patel K Smith BC Rowe LA 1993 09 01 Performance of a software MPEG video decoder Proceedings of the First ACM International Conference on Multimedia ACM Multimedia New York City Association for Computing Machinery 75 82 doi 10 1145 166266 166274 ISBN 978 0 89791 596 0 Reference 3 in the paper is to Committee Draft of Standard ISO IEC 11172 December 6 1991 a b ISO IEC 11172 3 1993 Information technology Coding of moving pictures and associated audio for digital storage media at up to about 1 5 Mbit s Part 3 Audio ISO 1993 Retrieved 2010 07 14 a b ISO IEC 13818 3 1995 Information technology Generic coding of moving pictures and associated audio information Part 3 Audio ISO 1995 Retrieved 2010 07 14 MPEG 1 and MPEG 2 Layer II Audio Encoding Partial draft Sustainability of Digital Formats Washington D C Library of Congress 17 May 2012 Retrieved 1 December 2021 a b c MPEG Audio FAQ Version 9 1998 Retrieved 2010 08 22 Techopedia MPEG 1 Audio Layer II MP2 techopedia com Retrieved 2022 03 17 A J Bower 1998 Digital Radio The Eureka 147 DAB System UK BBC Retrieved 2010 08 22 Dehery Y F Lever M Urcun P 1991 A MUSICAM source codec for digital audio broadcasting and storage Proceedings ICASSP 91 1991 International Conference on Acoustics Speech and Signal Processing pp 3605 3608 vol 5 doi 10 1109 ICASSP 1991 151054 ISBN 0 7803 0003 3 a b AES E Library Musicam Source Coding 1991 Retrieved 2010 08 22 Dehery Y F Lever M Urcun P May 1991 A MUSICAM source codec for Digital Audio Broadcasting and storage Proceedings ICASSP 91 1991 International Conference on Acoustics Speech and Signal Processing pp 3605 3608 doi 10 1109 ICASSP 1991 151054 Box Alan 1991 04 15 A DAB commentary from Alan Box EZ communication and chairman NAB DAB task force PDF Broadcasting Vol 150 no 15 p 26 Digital Audio Broadcasting DAB DAB to mobile portable and fixed receivers Details of DE JTC DAB Work Item ETS 300 401 1995 02 15 retrieved 2010 08 23 DAB Service planning for terrestrial Digital Audio Broadcasting PDF 1992 archived from the original PDF on 2005 05 04 retrieved 2010 08 22 a b Status report of ISO MPEG September 1990 1990 Archived from the original on 2010 02 14 Retrieved 2010 08 22 a b Telos Systems Facts about MPEG compression Archived from the original on 2001 05 08 Retrieved 2010 08 22 MUSICAM USA MUSICAM USA Frequently Asked Questions Isn t MUSICAM simply your implementation of ISO MPEG Layer 2 Retrieved 2010 08 23 Radio Broadcasting Systems Digital Audio Broadcasting DAB to mobile portable and fixed receivers Details of REN JTC DAB 36 Work Item EN 300 401 2006 06 15 retrieved 2010 08 23 Chiariglione Leonardo October 1989 MPEG Press Release Kurihama Moving Picture Experts Group Archived from the original on 2010 08 05 Digital Video and Audio Broadcasting Technology A Practical Engineering Guide Signals and Communication Technology ISBN 3 540 76357 0 p 144 In the year 1988 the MASCAM method was developed at the Institut fur Rundfunktechnik IRT in Munich in preparation for the digital audio broadcasting DAB system From MASCAM the MUSICAM masking pattern universal subband integrated coding and multiplexing method was developed in 1989 in cooperation with CCETT Philips and Matsushita Chiariglione Leonardo November 1991 MPEG Press Release Kurihama Moving Picture Experts Group Archived from the original on 2011 05 03 Retrieved 2010 07 17 ISO November 1991 CD 11172 3 Coding of Moving Pictures and Associated Audio for Digital Storage Media at up to About 1 5 MBit s Part 3 Audio neuron2 net Archived from the original DOC on June 11 2010 Retrieved 2010 07 17 Patel Ketan Smith Brian C Rowe Lawrence A Performance of a Software MPEG Video Decoder PDF ACM Multimedia 1993 Conference Article s reference 3 is ISO IEC JTC SC29 Coded Representation of Picture Audio and Multimedia Hypermedia Information Committee Draft of Standard ISO IEC 11172 December 6 1991 ISO 1992 11 06 MPEG Press Release London 6 November 1992 Chiariglione org Archived from the original on 12 August 2010 Retrieved 2010 07 17 a b Press Release Adopted at 22nd WG11 meeting Press release International Organization for Standardization 1993 04 02 Archived from the original on 2010 08 06 Retrieved 2010 07 18 ISO October 1998 MPEG Audio FAQ Version 9 MPEG 1 and MPEG 2 BC ISO Retrieved 2009 10 28 Brandenburg Karlheinz Bosi Marina February 1997 Overview of MPEG Audio Current and Future Standards for Low Bit Rate Audio Coding Journal of the Audio Engineering Society 45 1 2 4 21 Retrieved 30 June 2008 National Academey of Television Arts and Sciences Outstanding Achievement in Technical Engineering Development Awards PDF archived from the original PDF on 2010 04 14 retrieved 2010 08 01 CCETT DAB Digital Audio Broadcasting archived website 2001 02 11 Archived from the original on 2001 02 11 Retrieved 2010 08 01 Werner Oomen Leon van de Kerkhof MPEG 2 Audio Layer I II chiariglione org Retrieved 2009 12 29 a b Predrag Supurovic September 1998 MPEG Audio Frame Header Retrieved 2009 07 11 ISO MPEG Audio Subgroup MPEG Audio FAQ Version 9 MPEG 1 and MPEG 2 BC retrieved on 2009 07 11 TwoLAME MPEG Audio Layer II VBR retrieved on 2009 07 11 Sisvel We protect ideas MPEG Audio Introduction sisvel com Retrieved 2021 07 04 References EditGenesis of the MP3 Audio Coding Standard by Hans Georg Musmann in IEEE Transactions on Consumer Electronics Vol 52 Nr 3 pp 1043 1049 August 2006 MUSICAM Source Coding by Yves Francois Dehery AES 10th International Conference Kensington London England 7 9 Sept 1991 pp 71 79 External links EditThe history of MP3 from Fraunhofer IIS MPEG Audio Resources and Software TooLAME An MP2 encoder TwoLAME A fork of the tooLAME code RFC 3003 The document defining MIME type for MPEG 1 Audio Layer II A MPEG Audio Layer II decoder in 4k Source code for small open source decoder Official MPEG web site Patent Status of MPEG 1 H 261 and MPEG 2 Some information about patents Retrieved from https en wikipedia org w index php title MPEG 1 Audio Layer II amp oldid 1077824033, wikipedia, wiki, book, books, library,

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